C. That's a good idea! I can't agree with you more!

[calui]

I have a situation as follows:

Danny and Rosy are working on a plan for the weekend vacation.
Danny: "Both of us are keen on the beauty of nature, so let's go to the Kong Forest at Suoi Cat for the weekend!"
Rosy: " ______"
A. That sounds perfect! I am not really interested!
B. That doesn't sound great at all! I agree with you!
C. That's a good idea! I can't agree with you more!

The answer someone offers is C.
However, I don't agree with it. I have 2 questions to ask you as native speakers:
1. Do you use "I can't agree with you more." to give a response to such a situation when it looks like an invitation?
2. Is it true that "I can't agree with you more." is widely used to express agreemment? It isn't an idiom. Do native speakers use it to replace "I couldn't agree with you more."
I highly appreciate your answers. Thank you.

 

[Tarheel]

Since it is multiple choice, all you have to do is pick C and you win! (The others contradict themselves.)

I agree that "I couldn't agree with you more" is more natural. (Good job!)

 

[emsr2d2]

I agree that "I couldn't agree with you more" is more natural.

The same goes for BrE. I'm not sure I've ever heard anyone start that phrase with "I can't". It's always "I couldn't".

 

[calui]

Do you think that we can use either "I couldn't agree with you more." or "I can't agree with you more." for the situation with "let's go to the Kong Forest at Suoi Cat for the weekend!"?

 

[Tarheel]

@calui The expression is "I couldn't agree with you more," indicating enthusiastic agreement. However, in that context she is saying she'd be happy to go with him. So although C is the best choice, it's not what I would expect somebody to say.

Danny: Would you like to go with me to the beach for the weekend?
Mary: I'd love to!